Rotary impact tool

Abstract

To provide a rotary impact tool including an oil unit in which the oil unit can be protected against a temperature rise without measuring a temperature of the oil unit.SOLUTION: A rotary impact tool includes a motor, an output shaft, an oil unit, a motor control part, an impact state measurement part, a temperature estimation part, and a protection operation part. The impact state measurement part measures an impact state of the output shaft by an impact mechanism provided in the oil unit. The temperature estimation part estimates a temperature of the oil unit by integrating measurement results of the impact state by the impact state measurement part. When a temperature estimation value obtained by the temperature estimation part exceeds a preset protection threshold, the protection operation part performs protection operation of suppressing driving of the motor by the motor control part.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to a rotary impact tool equipped with an oil unit. [Background technology]

[0002] As described in Patent Document 1, a rotary impact tool including an oil unit that strikes an output shaft is known. The oil unit is rotated by a motor and includes a case filled with oil. The rotational torque of the case is transmitted to the output shaft via the oil, causing the output shaft to rotate. The oil unit case is also provided with a striking mechanism that forms a high-pressure oil chamber by using a rotational phase difference between the case and the output shaft to strike the output shaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5382291 Summary of the Invention [Problem to be solved by the invention]

[0004] In an oil unit, the striking mechanism generates heat due to friction with the oil each time it strikes. When this heat causes the oil unit to heat up, the oil expands, causing the accumulator inside the unit to collapse or oil to leak to the outside, resulting in an irreversible loss of performance. However, because the oil unit is a rotating body, it is difficult to measure its temperature directly, and it is difficult to measure the temperature of the oil unit and protect it from temperature increases.

[0005] For this reason, when using the rotary impact tool, the user must refrain from heavy work that places a large load on the output shaft or work slowly to prevent the oil unit from overheating and breaking down, which results in reduced work efficiency.

[0006] One aspect of the present disclosure aims to provide a rotary impact tool equipped with an oil unit that can protect the oil unit from a temperature rise without measuring the temperature of the oil unit. [Means for solving the problem]

[0007] A rotary impact tool according to one aspect of the present disclosure includes a motor, an output shaft to which a tool can be attached at its tip, an oil unit, a motor control unit, a temperature estimation unit, and a protection operation unit. The oil unit includes a case rotated by the motor and into which the rear end of the output shaft is rotatably inserted, oil sealed in the case, and an impact mechanism.

[0008] The oil unit's impact mechanism transmits the rotational torque of the case to the output shaft by oil to rotate the output shaft, and also creates a high-pressure oil chamber by the rotational phase difference between the case and the output shaft to impact the output shaft.

[0009] The motor control unit is configured to drive and control the motor in accordance with an external command, the impact state measurement unit is configured to measure the impact state of the output shaft by the impact mechanism, and the temperature estimation unit is configured to estimate the temperature of the oil unit by integrating the measurement results of the impact state by the impact state measurement unit.

[0010] The protective operation unit is configured to perform a protective operation of suppressing driving of the motor by the motor control unit when the temperature estimated value obtained by the temperature estimator exceeds a preset protective threshold value.

[0011] Therefore, according to the rotary impact tool of the present disclosure, by estimating the temperature of the oil unit from the impact state of the impact mechanism, it is possible to detect a temperature rise in the oil unit and protect the oil unit from the temperature rise.

[0012] Therefore, the user of the rotary impact tool does not need to refrain from heavy-load work or work slowly to prevent the oil unit from breaking down due to an increase in temperature, thereby improving work efficiency. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a side view of an impact driver according to a first embodiment. [Figure 2] 1 is a central vertical cross-sectional view of an impact driver according to a first embodiment. [Figure 3] FIG. 2 is an enlarged cross-sectional view taken along the line AA in FIG. [Figure 4] 4A is a central vertical cross-sectional view of the oil unit shown in FIG. 2, and FIG. 4B is a cross-sectional view taken along line BB in FIG. 4A. [Figure 5] 5A shows a cross section taken along line CC in FIG. 4, FIG. 5B shows a cross section just before impact, and FIG. 5C shows a cross section after impact. [Figure 6] FIG. 3 is a block diagram showing a circuit configuration of a controller shown in FIG. 2. [Figure 7] 7 is a flowchart showing a control process executed by the microcomputer shown in FIG. 6. [Figure 8] 8 is a flowchart showing the oil unit protection process executed in S240 of FIG. 7. [Figure 9] 9 is an explanatory diagram illustrating the configuration and usage procedure of a buffer used in the protection process of FIG. 8. [Figure 10] 10 is a flowchart showing a protection process for an oil unit according to a second embodiment. [Figure 11] 10 is a flowchart showing a protection process for an oil unit according to a third embodiment. [Figure 12] FIG. 12 is an explanatory diagram illustrating the operation of the protection process shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] [Summary of the embodiment] A rotary impact tool in one embodiment may include a motor, an output shaft to the tip of which a tool can be attached, and an oil unit.

[0015] The oil unit may include a case that is rotated by the motor and into which the rear end side of the output shaft is rotatably inserted, oil sealed in the case, and a striking mechanism. The impact mechanism may be configured to transmit the rotational torque of the case to the output shaft using oil to rotate the output shaft, and to create a high-pressure oil chamber by using a rotational phase difference between the case and the output shaft to impact the output shaft.

[0016] Additionally / alternatively, the rotary impact tool may include a motor control unit configured to drive and control the motor in accordance with an external command. Additionally / alternatively, the rotary impact tool may include an impact condition measuring unit configured to measure the impact condition of the output shaft by the impact mechanism.

[0017] Additionally or alternatively, the rotary impact tool may include a temperature estimation unit that estimates the temperature of the oil unit by accumulating the measurement results of the impact state by the impact state measurement unit. Additionally / alternatively, the rotary impact tool may include a protective operation unit configured to perform protective operation of suppressing driving of the motor by the motor control unit when the temperature estimated value obtained by the temperature estimation unit exceeds a predetermined protective threshold.

[0018] In one embodiment, if a rotary impact tool includes the above-mentioned motor, output shaft, oil unit, motor control unit, impact state measurement unit, temperature estimation unit, and protective operation unit, such a rotary impact tool can estimate the temperature of the oil unit from the impact state of the impact mechanism.

[0019] Therefore, with this rotary impact tool, a temperature rise in the oil unit can be detected from the estimation result and the oil unit can be protected from the temperature rise. Furthermore, the user of the rotary impact tool does not need to refrain from heavy work or work slowly to prevent the oil unit from breaking down due to a temperature rise. This improves the work efficiency when using the rotary impact tool.

[0020] Additionally / alternatively, the impact condition measuring unit may be configured to measure the number of impacts per predetermined time as the impact condition, and the temperature estimating unit may be configured to estimate the temperature of the oil unit by integrating the number of impacts measured by the impact condition measuring unit. With a rotary impact tool having the impact condition measuring unit and the temperature estimating unit configured in this manner, the temperature of the oil unit can be estimated based on the number of impacts of the impact mechanism on the output shaft.

[0021] Additionally / alternatively, the temperature estimation unit may be configured to subtract a cumulative value of the number of impacts when the number of impacts measured by the impact state measurement unit is equal to or less than a preset lower limit. With a rotary impact tool having a temperature estimation unit configured in this manner, the number of impacts is added or subtracted when accumulating the number of impacts, and it becomes possible to accurately estimate the temperature of the oil unit taking into account heat dissipation from the oil unit.

[0022] Additionally / alternatively, the temperature estimation unit may be configured to include a plurality of buffers configured to store the number of impacts measured by the impact state measurement unit, and each time the impact state measurement unit measures the number of impacts per predetermined time, the measured number of impacts is stored in the plurality of buffers in sequence, thereby updating the number of impacts in each buffer in sequence, and calculating the total number of impacts stored in the plurality of buffers as the temperature estimation value of the oil unit.

[0023] In a rotary impact tool having a temperature estimation unit configured as described above, the number of impacts per predetermined time is stored in the multiple buffers in order, and the total number of impacts stored in each buffer is the average number of impacts within a period obtained by multiplying the predetermined time by the number of buffers, which represents the frequency of impacts. Therefore, the temperature of the oil unit is estimated based on the frequency of impacts, and the estimation accuracy can be improved.

[0024] Additionally / alternatively, the temperature estimation unit may be configured to have two systems of buffer groups with different numbers of buffers, and to store the number of impacts and calculate the total number of impacts for each buffer group, and the protection operation unit may be configured to compare the total number of impacts calculated by the temperature estimation unit using the two systems of buffer groups with a protection threshold value previously set for each buffer group, and to perform protection operation when either of the total numbers of impacts exceeds the corresponding protection threshold value.

[0025] With a rotary impact tool having a temperature estimation unit and a protective operation unit configured in this manner, it is possible to properly estimate the temperature of the oil unit and protect the oil unit from temperature rise, regardless of whether the work using the rotary impact tool is heavy-load work or medium-load work.

[0026] In other words, the number of impacts per task differs between heavy-load and medium-load work, with the number of impacts per task being higher during heavy-load work than during medium-load work. As a result, when each task is performed repeatedly, the time during which protection due to temperature rise is desired to be activated is shorter during heavy-load work than during medium-load work, and the total number of impacts detected within that time is lower during heavy-load work than during medium-load work.

[0027] Therefore, if a common buffer is used to calculate the total number of impacts during heavy load work and medium load work, it may not be possible to protect the oil unit from temperature rise during heavy load work or medium load work.

[0028] However, as described above, by determining the temperature rise of the oil unit using two buffer groups and protection thresholds set for each buffer group, it becomes possible to properly determine the temperature rise of the oil unit whether the work is heavy load or medium load.

[0029] Additionally / alternatively, the protective operation unit may be configured to determine whether the latest value of the number of impacts stored in the multiple buffers is equal to or less than a predetermined lower limit number when the total number of impacts stored in the multiple buffers exceeds a protective threshold, and not to perform protective operation when the latest value of the number of impacts is equal to or less than the lower limit number.

[0030] With a rotary impact tool having a protective operation unit configured in this manner, it is possible to prevent the protective operation from being performed when the most recent number of impacts is below a lower limit value and the temperature of the oil unit has not risen due to heat dissipation from the oil unit over the course of a specified time.

[0031] Additionally / alternatively, the impact condition measurement unit may be configured to measure the number of impacts per predetermined time as the impact condition, and the temperature estimation unit may be configured to estimate the temperature of the oil unit by taking a weighted average of the number of impacts measured by the impact condition measurement unit, and to switch the gain used for the weighted average depending on whether the number of impacts is greater than or equal to a threshold value.

[0032] In a rotary impact tool having the impact state measuring unit and the temperature estimating unit configured as described above, the number of impacts measured by the impact state measuring unit is weighted-averaged, so that the frequency of impacts by the impact mechanism can be estimated without using the above-mentioned multiple buffers. In addition, since the gain used for the weighted averaging is switched depending on the number of impacts, by setting the gain in accordance with the temperature rise characteristics of the oil unit due to impacts, it is possible to more accurately estimate the temperature of the oil unit.

[0033] Additionally / alternatively, the impact condition measuring unit may be configured to measure, as the impact condition, a current flowing through the motor per predetermined time, and the temperature estimating unit may be configured to estimate the temperature of the oil unit by integrating the current measured by the impact condition measuring unit. With a rotary impact tool having the impact condition measuring unit and the temperature estimating unit configured in this manner, the temperature of the oil unit can be estimated based on the current flowing through the motor.

[0034] In other words, when an impact occurs, a load is applied to the motor from the output shaft, and the current flowing through the motor becomes larger than when the motor is operating without a load. Furthermore, when an impact occurs, the current flowing through the motor also becomes larger. Therefore, even if the impact state is measured by measuring the current flowing through the motor rather than the number of impacts, the temperature of the oil unit can be estimated from the measurement results, and the oil unit can be protected from a temperature rise.

[0035] Additionally / alternatively, the temperature estimating unit may be configured not to integrate the current measured by the impact state measuring unit when the current is equal to or less than a preset lower limit current. With a rotary impact tool having a temperature estimating unit configured in this manner, it is possible to more accurately estimate the temperature of the oil unit based on the current flowing through the motor.

[0036] In other words, when the motor is operating without load, no load is applied to the motor, so the current flowing therethrough is small. In this state, no impacts occur, so the temperature of the oil unit does not rise due to impacts. It is also possible that the oil unit is cooled by the airflow generated by the rotation of the motor, lowering its temperature. Therefore, as described above, by not integrating the current when the current flowing through the motor is below the lower limit current, the temperature of the oil unit can be estimated more accurately.

[0037] Additionally / alternatively, the protective operation unit may be configured to prohibit the motor control unit from driving the motor as the protective operation. In a rotary impact tool having a protective operation unit configured in this manner, when a temperature rise in the oil unit is detected, the protective operation unit prohibits the motor from driving, thereby suppressing a temperature rise in the oil unit due to impact and protecting the oil unit from the temperature rise.

[0038] Additionally / alternatively, the protective operation unit may be configured to notify the user that the protective operation is being performed when the motor control unit is prohibited from driving the motor by the protective operation. In a rotary impact tool having the protective operation unit configured in this manner, when the temperature rise of the oil unit is detected and driving of the motor is prohibited, the user can be notified of the reason why the motor has stopped, thereby preventing the user from feeling uncomfortable.

[0039] Additionally / alternatively, the protective operation unit may be configured to notify a temperature rise of the oil unit as a protective operation. With a rotary impact tool having such a protective operation unit, when a temperature rise of the oil unit is detected, the protective operation unit notifies the user of the temperature rise and urges the user to refrain from working with the rotary impact tool. Therefore, this configuration also makes it possible to prevent the oil unit from breaking down due to a temperature rise.

[0040] Additionally / alternatively, the protective operation unit may be configured to cancel the implementation of the protective operation when a preset waiting time has elapsed since the start of the protective operation. In a rotary impact tool having a protective operation unit configured in this manner, when the temperature of the oil unit no longer rises due to the protective operation, the oil unit is cooled by outside air, so that by canceling the protective operation after the waiting time has elapsed, the user can quickly resume work.

[0041] Additionally / alternatively, the rotary impact tool may include a protection threshold setting unit configured to set the protection threshold in accordance with the ambient temperature of the rotary impact tool. With a rotary impact tool configured in this manner, the protection threshold can be set such that, for example, the protection threshold is increased in an environment where the ambient temperature is low and the oil unit is unlikely to heat up, and the protection threshold is decreased in an environment where the ambient temperature is high and the oil unit is likely to heat up. Therefore, it is possible to more appropriately detect a temperature rise in the oil unit in accordance with the ambient environment.

[0042] Additionally / alternatively, the protection threshold setting unit is configured to set the protection threshold in accordance with the ambient temperature at the time of start-up of the rotary impact tool. With a rotary impact tool having a protection threshold setting unit configured in this manner, even if the temperature of the rotary impact tool rises due to use of the rotary impact tool, the protection threshold is set in accordance with the ambient temperature at the time of start-up, in other words, the environmental temperature, and it becomes possible to more appropriately detect the temperature rise of the oil unit.

[0043] Specific Exemplary Embodiments Exemplary embodiments of the present disclosure will be described below in conjunction with the drawings. [First embodiment] [composition] In this embodiment, a rechargeable impact driver 1 will be described as an example of the rotary impact tool of the present disclosure.

[0044] As shown in Figures 1 and 2, the impact driver 1 of this embodiment has a main body 2 and a grip 3. The main body 2 extends with its central axis in the front-to-rear direction and houses a brushless motor 20 and an oil unit 22. The grip 3 protrudes downward from the main body 2. A battery attachment section 4 is provided at the lower end of the grip 3. A battery pack 5, which serves as a power source, can be attached to the battery attachment section 4 from the front.

[0045] The housing of the impact driver 1 includes a main body housing 6 and a unit case 7. The main body housing 6 integrates the rear of the main body 2, the grip 3, and the battery attachment section 4. The unit case 7 is a tapered cylinder that is attached to the front of the main body housing 6 and forms the front of the main body 2. The main body housing 6 is formed by assembling a pair of left and right half housings 6A and 6B shown in FIG. 3 with screws 8. A resin case cover 9 is attached to the outside of the unit case 7. A rubber bumper 10 is attached to the front of the case cover 9.

[0046] A trigger switch 11 is housed in the upper part of the grip part 3. The trigger switch 11 has a trigger 12 protruding forward. A forward / reverse switch button 13 for switching the rotation of the brushless motor 20 is provided above the trigger switch 11. Also, a light 14 is provided to illuminate the area in front of the main body part 2.

[0047] A terminal block 15 is housed within the battery mounting section 4. The terminal block 15 is electrically connected to the battery pack 5. A controller 16 is disposed above the terminal block 15. The controller 16 includes a control circuit board 17 and is disposed parallel to the terminal block 15. A switch panel 18 is provided above the controller 16.

[0048] The switch panel 18 is provided with various switches such as a changeover switch for turning on and off the light 14. The switch panel 18 is exposed on the top surface of the battery mounting portion 4.

[0049] The switch panel 18 is also provided with a display unit 19 for indicating the operating status and battery status of the impact driver. The display unit 19 includes an LED that indicates motor stoppage due to a temperature rise in the oil unit 22 and issues a warning before the motor stops.

[0050] The main body 2 accommodates, in order from the rear, a brushless motor 20, a reduction mechanism 21, and an oil unit 22. A spindle 23 serving as an output shaft is rotatably mounted on the oil unit 22. The front end of the spindle 23 protrudes forward from the oil unit 22, and a tool such as a driver bit can be attached to the tip of the spindle 23.

[0051] Brushless motor 20 is an inner rotor type having rotor 25 inside cylindrical stator 24. As shown in FIG. 3, stator 24 has cylindrical stator core 26. Stator core 26 is formed from a plurality of laminated steel plates. Stator 24 also has insulators 27, 27. Insulators 27, 27 are fixed to the front and rear end faces of stator core 26 in the axial direction, respectively.

[0052] The stator 24 also has a plurality of coils 28, 28.... The plurality of coils 28, 28... are wound around the stator core 26 via insulators 27, 27. Each coil 28 is electrically connected to a fusing terminal held by the insulator 27, thereby forming a three-phase connection.

[0053] A sensor circuit board 29 is attached to the front insulator 27. The sensor circuit board 29 includes a rotational position detection unit 29A that detects the position of a sensor permanent magnet 33 provided on the rotor 25 to detect the rotational position of the rotor 25. The rotational position detection unit 29A is configured with, for example, a wheel element, and outputs a rotation detection signal for each predetermined rotation angle of the rotor 25.

[0054] The rotor 25 includes a rotating shaft 30 and a rotor core 31. The rotating shaft 30 is provided at the axis of the rotor core 31. The rotor core 31 is arranged cylindrically around the rotating shaft 30. The rotor core 31 is made by laminating a plurality of steel plates. Cylindrical permanent magnets 32, 32... are fixed to the rotor 25. The permanent magnets 32, 32... are arranged outside the rotor core 31 with alternating polarities.

[0055] Additionally, permanent magnets 33, 33... for the rotational position detection unit 29A are fixed to the rotor 25. These permanent magnets 33, 33... are fixed radially in front of the permanent magnets 32, 32.... Therefore, the rotational position detection unit 29A can detect the rotational position of the rotor 25 from changes in the magnetic flux from the permanent magnets 33, 33... that accompany the rotation of the rotor 25.

[0056] Next, the rear end of the rotating shaft 30 is held by a bearing 34. The bearing 34 is held on the inner surface of the rear part of the main body housing 6. A fan 35 is attached to the rotating shaft 30 in front of the bearing 34. A plurality of exhaust ports 36, 36... are formed outside the fan 35 on the left and right side surfaces of the main body 2.

[0057] Front air intake ports 37A are formed on the left and right side surfaces of the main body 2 in front of the exhaust port 36. The front air intake ports 37A are formed at the left and right rear ends of the case cover 9. In addition, multiple rear air intake ports 37B, 37B... are formed behind the front air intake port 37A. The rear air intake ports 37B are formed at a position that hits the outside of the front part of the brushless motor 20.

[0058] A gear case 38 is held in front of the brushless motor 20 within the main housing 6. The gear case 38 is disk-shaped and includes a bearing holder 39. The bearing holder 39 supports the front end of the rotating shaft 30 via a bearing 40. A pinion 41 is attached to the front end of the rotating shaft 30. The pinion 41 penetrates the gear case 38 and protrudes forward.

[0059] The reduction mechanism 21 includes an internal gear 42, a plurality of planetary gears 43, 43..., and a carrier 44. The internal gear 42 is fixed to the front part of the gear case 38. The plurality of planetary gears 43, 43... mesh with the inside of the internal gear 42. The carrier 44 supports the planetary gear 43.

[0060] The front end of the internal gear 42 is inserted into the rear end of the unit case 7. The front end of the internal gear 42 also supports a rear case 51 of the oil unit 22 via a bearing 45 held inside. The multiple planetary gears 43, 43... are disposed around the pinion 41 and mesh with the pinion 41. The carrier 44 is connected to the rear case 51 of the oil unit 22.

[0061] [Oil unit explanation] As shown in Fig. 4, the oil unit 22 includes a front case 50, a rear case 51, and the spindle 23. The front case 50 is disposed inside the unit case 7 and is cylindrical and gradually tapered toward the front. A retaining hole 53 through which the spindle 23 passes is formed in the front end 52. A seal member 52A is provided between the front end 52 and the spindle 23.

[0062] A pair of screw holes 54, 54 are formed through the front end 52 radially outward of the retaining hole 53. A screw 55 serving as a stopper is threaded into each screw hole 54 from the front. A ring-shaped front chamber 56 is formed on the inner surface of the front end 52. The front chamber 56 communicates with each screw hole 54. A tube 57 is housed within the front chamber 56. The tube 57 is hollow and filled with air, and is housed in a ring shape within the front chamber 56. A partition plate 58 is provided behind the tube 57. The partition plate 58 has a plurality of notches 59, 59... on its outer periphery. A rear chamber 60 is formed behind the partition plate 58, and the front chamber 56 and rear chamber 60 communicate with each other via the notches 59.

[0063] The rear case 51 includes a central portion 61 and side wall portions 62. The central portion 61 has a disk shape that is supported by the bearing 45. The side wall portions 62 have a cylindrical shape that protrudes forward from the periphery of the central portion 61.

[0064] The side wall portion 62 is screwed into the front case 50 from the rear and coupled to the front case 50. A seal member 62A is provided between the side wall portion 62 and the front case 50. The front end of the side wall portion 62 abuts against the partition plate 58. A step portion 63 is provided on the inner surface of the front case 50, and the partition plate 58 is fixed between the side wall portion 62 and the step portion 63.

[0065] 5, a pair of protrusions 64, 64 are formed on the inner peripheral surface of the side wall portion 62. These protrusions 64, 64 are arranged in point symmetry about the axis of the rear case 51 and protrude toward the center. Each of the protrusions 64, 64 has a tapered cross-sectional shape whose circumferential width narrows toward the center.

[0066] A recess 65 is formed in the center of the central portion 61. The recess 65 is recessed in two stages, with the center being deeper and the outer edges becoming shallower. A cam 66 is fixed facing forward in the center of the recess 65. The rear portion of this cam 66 forms a two-face width portion 66A.

[0067] The front portion of the cam 66 is a flat portion 66B that gradually becomes thinner from the thickest center toward the outside in the radial direction. The two-face width portion 66A and the flat portion 66B are oriented perpendicular to the line connecting the centers of the protrusions 64, 64 in a front view.

[0068] As shown in Figure 4, the spindle 23 has a through hole 23A at its axis. The rear of the through hole 23A forms an internal pressure chamber 67 located within the rear chamber 60. The internal pressure chamber 67 has a circular cross section, and a cam 66 is inserted therein so as to be relatively rotatable. The rear end of the spindle 23 is supported by a recess 65 in the rear case 51 outside the cam 66. The middle portion of the spindle 23 is supported by the unit case 7 via a bearing 68 (see Figures 2 and 3).

[0069] The front portion of the through hole 23A is an attachment hole 69 into which a tool bit is inserted. A sleeve 70 for attaching and detaching the tool bit is provided on the outside of the attachment hole 69. An output adjustment plug 71 is disposed behind the attachment hole 69 so as to close the attachment hole 69. The output adjustment plug 71 is screwed into the through hole 23A.

[0070] Here, a sealed space including the front chamber 56 and the rear chamber 60 is formed by the front case 50, the rear case 51, the screw 55, the spindle 23, the output adjustment plug 71, etc. Oil is sealed in this sealed space. This oil sealing is performed through the screw hole 54. The oil pressure can be changed by adjusting the position of the output adjustment plug 71 by rotating it with a tool such as a screwdriver inserted into the through hole 23A from the front.

[0071] 5, the rear portion 72 of the spindle 23 has a flat cross-sectional shape that extends in the diameter direction of the rear case 51. However, the longitudinal dimension of the rear portion 72 is shorter than the dimension between the opposing surfaces of the protrusions 64, 64 of the rear case 51.

[0072] The rear portion 72 is located between the partition plate 58 and the central portion 61 of the rear case 51. A front communicating hole 73 and a rear communicating hole 74 are formed in the front and rear surfaces of the rear portion 72, respectively, in the radial direction of the spindle 23. The front communicating hole 73 communicates the through-hole 23A with the rear chamber 60 when the rear portion 72 is in contact with the partition plate 58. The rear communicating hole 74 communicates the through-hole 23A with the rear chamber 60 when the rear portion 72 is in contact with the central portion 61.

[0073] A pair of holes 86, 86 are formed on the outer side of the cam 66 within the rear portion 72 of the spindle 23. The holes 86, 86 are formed in the diameter direction of the spindle 23 and communicate with the through-hole 23a. A ball 85 is housed in each hole 86. Each ball 85 is movable radially within the hole 86 and can come into contact with the flat portion 66B of the cam 66 when it moves toward the center.

[0074] A pair of retaining grooves 80, 80 are formed at both longitudinal ends of the rear portion 72. The retaining grooves 80, 80 communicate with holes 86, 86. The retaining grooves 80, 80 are formed to penetrate the rear portion 72 in the front-to-rear direction so as to open at both longitudinal ends and at the front and rear.

[0075] A blade 81 is disposed in each retaining groove 80. Each blade 81 has a width that fits approximately within the circumferential width of the retaining groove 80 and a length that fits over the entire length of the retaining groove 80 in the front-to-rear direction. Each blade 81 is held within the retaining groove 80 so as to be movable in the radial direction of the spindle 23. The radially outer end of each blade 81 is tapered, with the width decreasing as it moves radially outward. Each blade 81 is capable of contacting a ball 85 when it moves toward the center.

[0076] On the inner end surfaces of the blades 81, bosses 88, 88 are formed at positions facing the balls 85, 85, protruding inward from the end surfaces. The axis of each boss 88 coincides with a line passing through the center of each ball 85 in the radial direction of the spindle 23. In other words, the balls 85, 85 and the bosses 88, 88 are aligned in the radial direction of the spindle 23.

[0077] A ring-shaped groove 89 is formed on the radially inner end surface of each blade 81 at a position where the base of the bosses 88 meets the base of the bosses 88. Coil springs 78 are fitted onto the bosses 88 of the blades 81, and one end of each coil spring 78 is inserted into the groove 89.

[0078] The inner diameter of the coil springs 78, 78 is larger than the outer diameter of the balls 85, 85. The other end of each coil spring 78 opposite the groove 89 abuts against the bottom 80A of the retaining groove 80 around the ball 85. Therefore, each blade 81 is pushed outward in the radial direction from the retaining groove 80 due to the biasing force of the coil spring 78 and the movement of the ball 85 outward in the radial direction.

[0079] That is, when the flat portion 66b of the cam 66 is oriented parallel to the longitudinal cross section of the rear portion 72 within the internal pressure chamber 67 of the rear portion 72, the balls 85 are pushed radially outward by the cam 66. At the same time, the balls 85 are also pushed radially outward by the balls 85.

[0080] At this time, the blades 81, 81 are close to the inner circumferential surface of the rear case 51 but do not contact the inner circumferential surface, and are positioned so as to interfere with the protrusions 64, 64 in the circumferential direction. However, because the coil springs 78, 78 are arranged around the balls 85, 85, the blades 81, 81 are urged to a position where they move away from the balls 85, 85 and abut against the inner circumferential surface of the rear case 51.

[0081] [Explanation of impact driver operation] The operation of the impact driver 1 configured as above will now be described. A user grasps the grip portion 3 and pulls the trigger 12. This turns on the trigger switch 11, causing a three-phase current to be supplied from the battery pack 5 to the stator 24 of the brushless motor 20, causing the rotor 25 to rotate. That is, the controller 16 obtains a rotation detection signal output from the rotational position detection unit 29A of the sensor circuit board 29 and acquires the rotational state of the rotor 25. Then, the controller 16 passes a three-phase current sequentially through each coil 28 of the stator 24 according to the acquired rotational state. This causes the rotor 25 and the rotating shaft 30 to rotate.

[0082] The rotation of the rotary shaft 30 is transmitted to the planetary gears 43, 43... via the pinion 41. The rotation is then reduced in speed by the planetary gears 43, 43... that revolve within the internal gear 42, and transmitted from the carrier 44 to the rear case 51 of the oil unit 22.

[0083] In the oil unit 22, the cam 66 rotates in the direction of the arrow together with the rear case 51. As a result, the flat portion 66b of the cam 66 pushes the blades 81, 81 in the direction of protrusion from the rear portion 72 via the balls 85, 85. At this time, the biasing force of the coil spring 78 also adds to the pushing force.

[0084] As the rotation continues, the cam 66 opens the communication between the communication hole 74 and the internal pressure chamber 67, and oil flows into the internal pressure chamber 67. As a result, oil flows from each hole 86 to each holding groove 80, which promotes the pushing out of the balls 85, 85 and the blades 81, 81.

[0085] When the cam 66 further rotates together with the rear case 51 and reaches a phase where the cam 66 is parallel to the rear portion 72, the cam 66 pushes the balls 85 and the blades 81 to the outermost positions, as shown in Fig. 5A. At this pushed-out position of the blades 81, the tips of the blades 81 do not reach the inner peripheral surface of the rear case 51.

[0086] However, at high temperatures, the biasing force of the coil springs 78 pushes each blade 81 further radially outward away from the ball 85. Then, when the rear case 51 and cam 66 continue to rotate and the protrusions 64 collide with the blades 81, the cam 66 closes the space between the rear communicating hole 74 and the internal pressure chamber 67, as shown in FIG. 5B.

[0087] As a result, the oil pressure in the internal pressure chamber 67 increases, causing the internal pressure chamber 67 to become the high-pressure chamber of the present disclosure, and the blades 81 are held in the pushed-out position. As a result, the protrusions 64 collide with the blades 81, generating an impact torque on the spindle 23. In other words, the spindle 23, which is the output shaft, is struck.

[0088] At the time of this impact, even if the viscosity of the oil is low, the blades 81, 81 retract with a large stroke from the position where they reach the inner circumferential surface of the rear case 51, and the biasing force of the coil springs 78, 78 also acts as resistance to the retraction, thereby suppressing a decrease in impact torque.

[0089] After the impact torque is generated, the blades 81 are guided by the tapered surfaces of the protrusions 64 and the blades 81, causing the blades 81 to retreat toward the center. Therefore, as shown in FIG. 5C , the retracted blades 81 move relatively over the protrusions 64. Then, when the protrusions 64 pass the blades 81, the rotation of the rear case 51 and the cam 66 opens the space between the rear communicating hole 74 and the internal pressure chamber 67. Therefore, the cam 66 again pushes out the blades 81 via the balls 85.

[0090] Therefore, when a load is applied from the tool bit to the spindle 23 and the rotation of the spindle 23 stops or slows down, the above-mentioned process is repeated, resulting in two impact torques occurring per rotation of the rear case 51.

[0091] In the impact driver 1 of this embodiment, when the temperature of the oil unit 22 is low and the viscosity of the oil is high, the stroke of the blades 81 is ensured by the cam 66 and the balls 85. In other words, the required torque is obtained.

[0092] On the other hand, when the temperature of the oil unit 22 is high and the viscosity of the oil is low, the biasing force of the coil springs 78 can increase the resistance when the blades 81 collide with the protrusions 64 and move back. In other words, torque reduction is suppressed.

[0093] Therefore, the torque of the oil unit 22 is leveled regardless of temperature changes, thereby maintaining good work efficiency. In this embodiment, the protrusion 64, cam 66, coil spring 78, ball 85, and blade 81 in the oil unit 22 correspond to the impact mechanism of the present disclosure.

[0094] In the oil unit 22, the protrusions 64, 64 of the rear case 51 collide with the blades 81, 81, generating an impact torque in the spindle 23, and this collision occurs frequently when a load is applied from the tool bit to the spindle 23. In other words, in the oil unit 22, when a load is applied from the tool bit to the spindle 23 and a phase difference occurs in the rotations of the rear case 51 and the spindle 23, the spindle 23 is struck, and collisions frequently occur when tightening screws, for example.

[0095] Furthermore, since heat is generated during a collision, as the number of impacts due to collisions increases, the temperature of the oil unit 22 rises, leading to performance degradation due to oil leakage caused by oil expansion and failure of pressure adjustment members.

[0096] Therefore, in this embodiment, the controller 16 that drives and controls the brushless motor 20 measures the number of strikes of the spindle 23 per predetermined time, and estimates the temperature of the oil unit 22 from the measurement result.

[0097] When the estimated temperature reaches a predetermined high temperature judgment value, the rotation of brushless motor 20 is stopped and a notification to that effect is given to the user. An alarm is also given before the rotation is stopped. The notification of rotation stop or the issuance of the alarm is given, for example, by lighting or blinking an LED for anomaly notification or alarm generation on display unit 19 provided on switch panel 18.

[0098] [Controller Configuration] As shown in FIG. 6, the controller 16 includes a microcomputer (hereinafter referred to as "microcomputer") 100 including a CPU 102, a ROM 104, a RAM 106, etc., a motor driving unit 110, a current detecting unit 120, and a temperature detecting unit .

[0099] The motor driving unit 110 includes a bridge circuit having six switching elements respectively provided on the current paths between the coils 28 of each phase connected in three phases in the brushless motor (hereinafter referred to as the motor) 20 and the positive and negative poles of the battery pack 5.

[0100] The bridge circuit is a well-known drive circuit also known as an inverter circuit, and the microcomputer 100 controls the current flowing through the motor 20 by PWM-controlling the switching elements of the bridge circuit so that the rotation of the motor 20 reaches a target rotation speed. The target rotation speed is set according to the amount of pulling of the trigger 12, etc.

[0101] The current detection unit 120 is a detection circuit that detects the motor current supplied to the motor 20 via the motor drive unit 110, and includes, for example, a resistor for current detection provided in the current path to the motor 20.

[0102] The temperature detection unit 130 is a detection circuit that detects the temperature of the controller 16, and includes, for example, a thermistor for temperature detection. The temperature detection signal (hereinafter referred to as the temperature detection signal) detected by the temperature detection unit 130 is input to the microcomputer 100 together with the motor current detection signal (hereinafter referred to as the current detection signal) detected by the current detection unit 120 and the rotation detection signal from the rotation position detection unit 29A.

[0103] The microcomputer 100 is also connected to the trigger switch 11, forward / reverse switching button 13, light 14, switch panel 18, and display unit 19 of the switch panel 18. When the trigger switch 11 is turned on, the microcomputer 100 rotates the motor 20 according to the pulling amount of the trigger 12 and the rotation direction set by the forward / reverse switching button 13.

[0104] Furthermore, the microcomputer 100 turns on the light 14 and switches the target rotation speed of the motor 20 between high speed and low speed, depending on the state of various switches provided on the switch panel 18.

[0105] Furthermore, the microcomputer 100 detects the impact of the oil unit 22 on the spindle 23 from the motor current detected by the current detector 120 or the rotational fluctuation of the motor 20 obtained from the rotation detection signal from the rotational position detector 29A.

[0106] The temperature of the spindle 23 is estimated from the number of strikes within a predetermined period, in other words, the strike frequency, and the oil unit 22 is protected by stopping the rotation of the motor 20 or issuing an alarm.

[0107] [Control processing] Next, the control process executed by the microcomputer 100 to drive the motor 20 and protect the oil unit 22 will be described.

[0108] As shown in FIG. 7, this control process is carried out by repeatedly executing the processes of S210 to S260 (S represents step) at a predetermined control cycle (for example, every few milliseconds).

[0109] That is, first, in S210, the microcomputer 100 executes a switch detection process for acquiring various commands input from the trigger switch 11, the forward / reverse switching button 13, and the switches provided on the switch panel 18.

[0110] In the next step 220, analog signals such as the current detection signal from the current detection unit 120 and the temperature detection signal from the temperature detection unit 130 are converted into digital data, and an A / D conversion process is performed to obtain the motor current and the temperature of the controller 16.

[0111] In addition, in the A / D conversion process, based on the temperature of the controller 16 obtained from the temperature detection signal immediately after the microcomputer 100 is started, an alarm judgment value TH1 and a high temperature judgment value TH2 are set, which are used to determine the temperature rise of the oil unit 22 in the oil unit protection process described below.

[0112] In other words, the temperature of the controller 16 immediately after the microcomputer 100 is started corresponds to the ambient temperature of the impact driver 1, and the higher the ambient temperature, the more likely the oil unit 22 will rise in temperature, so the warning determination value TH1 and high temperature determination value TH2 are set low.

[0113] The warning determination value TH1 and the high temperature determination value TH2 correspond to the protection thresholds of the present disclosure. Furthermore, since these protection thresholds are set in the A / D conversion process of S220 according to the temperature of the controller 16, the A / D conversion process corresponds to the protection threshold setting unit of the present disclosure.

[0114] Next, in S230, the CPU 10 executes a process of measuring the number of strikes, which detects strikes on the spindle 23 by the oil unit 22 from the change in the motor current acquired in the A / D conversion process in S220 and counts the number of strikes.

[0115] In S240, an abnormality detection process is executed to detect various abnormalities in the impact driver 1. In this abnormality detection process, abnormal rotation of the motor 20 is detected based on the rotation detection signal, abnormal battery voltage supplied from the battery pack 5 is detected, and abnormal temperature rise of the controller 16 is detected based on the temperature detection signal.

[0116] The abnormality detection process in S240 also includes a protection process for the oil unit 22, which estimates the temperature of the oil unit 22 based on the number of strikes counted in S230 and determines whether the temperature of the oil unit 22 has increased.

[0117] Next, in S250, a motor control process is executed to PWM-control the switching elements of the bridge circuit constituting the motor drive unit 110 so that the rotation speed of the motor 20 calculated from the rotation detection signal input from the rotation position detection unit 29A becomes the target rotation speed.

[0118] This motor control process controls the current flowing through the motor 20 to drive the motor 20, but if an abnormality is detected in the abnormality detection process of S240, the power to the motor 20 is cut off and the drive of the motor 20 is stopped.

[0119] In addition, in S260, a display process is executed to notify of an abnormality detected in the abnormality detection process of S240 or to issue an alarm by displaying the control state of the motor 20 on the display unit 19 or by lighting or blinking various LEDs provided on the display unit 19. Then, after executing the display process of S260, the microcomputer 100 returns to the switch detection process of S210 and repeatedly executes the processes of S210 to S260.

[0120] Next, the protection process for the oil unit 22, which is executed as part of the abnormality detection process at S240, will be described. 8, in the protection process for the oil unit 22, first, in S310, it is determined whether a predetermined time T (for example, 1 second) has elapsed since the previous process of S320 or later was started. If it is determined in S310 that the predetermined time T has not elapsed, the process proceeds to S430.

[0121] If it is determined in S310 that the predetermined time T has elapsed, the process proceeds to S320, and during the elapse of the predetermined time T, the number of hits is counted in the hit count measurement process of S230, and it is determined whether the number of hits has been updated to a value greater than 0.

[0122] If it is determined in S320 that the number of hits has been updated to a value greater than 0 during the lapse of the predetermined time T, the process proceeds to S330. In S330, the updated current number of hits X (i.e., the count value of the number of hits) is saved in one of n buffers set in RAM 106 for storing the number of hits, the number of hits counted in S230 is set to the initial value: 0, and the process proceeds to S350.

[0123] If it is determined in S320 that the number of hits has not been updated to a value greater than 0 within the predetermined time T, the process proceeds to S340. In S340, the current count value of the number of hits, 0, is saved in one of n buffers set in RAM 106 for storing the number of hits, and the process proceeds to S350.

[0124] As shown in FIG. 9, the n buffers are used to store, in order, the count values ​​X1, 0, X2, . . . of the number of hits, which are counted each time a predetermined time T has elapsed since the microcomputer 100 was started up.

[0125] Then, in S320, the count value of the number of hits is written in the first buffer to the nth buffer in order every time a predetermined time T has passed. Also, in S320, when a predetermined period (n×T) determined by the predetermined time T and the number of buffers n has passed and the count value of the number of hits has been written in the nth buffer, after the predetermined time T has passed, the most recent count value of the number of hits is written in the first buffer. Then, thereafter, every time the predetermined time T has passed, the count value of the number of hits is rewritten with the most recent value in order from the second buffer to the nth buffer.

[0126] Therefore, the total number of hits stored in the n buffers is the most recent number of hits counted within a specified period (n x T) determined by the specified time T and the number of buffers n, in other words, a value representing the frequency of hits per specified period.

[0127] In S350, the total number of impacts AD stored in the n buffers is calculated as the estimated temperature value of the oil unit 22. In addition, in S360, it is determined whether the total number of impacts AD calculated as the estimated temperature value in S350 exceeds a preset warning determination value TH1.

[0128] If it is determined in S360 that the total number of hits AD exceeds the warning threshold TH1, the process proceeds to S370, where an warning request flag is set. The warning request flag is used to notify the user of the temperature rise of the oil unit 22 in response to the display process of S260, and if the warning request flag is set in the display process of S260, the warning LED is turned on or flashes.

[0129] As a result, the user can detect a temperature rise in the oil unit 22 and drive the motor 20 without load, thereby allowing the rotation of the fan 35 to cool the oil unit 22.

[0130] Next, in S370, when the warning request flag is set, the process proceeds to S380, where it is determined whether the total number of hits AD calculated as the temperature estimate in S350 has exceeded a high temperature determination value TH2 that is greater than the warning determination value TH1.

[0131] Then, if it is determined in S380 that the total number of impacts AD exceeds the high temperature determination value TH2, the process proceeds to S390, where it is determined whether the latest number of impacts X, the value of which is updated in the buffer in S330, is greater than the preset temperature rise determination value Y.

[0132] This temperature rise determination value Y is set to determine whether the number of strikes X counted within the most recent predetermined time T is the number of strikes that will raise the temperature of the oil unit 22. In other words, if the number of strikes X is small, the temperature of the oil unit 22 may not rise due to the cooling effect of the rotation of the fan 35, so in S390 it is determined whether the number of strikes X is greater than the number of strikes that will raise the temperature of the oil unit 22.

[0133] If it is determined in S390 that the number of hits X is greater than the temperature rise determination value Y, the process proceeds to S400, where the high temperature detection flag is set, and the process proceeds to S430. The high temperature detection flag is one of the abnormality detection flags that is set when an abnormality is detected in the abnormality detection process of S240, and when the high temperature detection flag is set, the driving of the motor 20 is stopped in the motor control process of S250. As a result, the temperature rise of the oil unit 22 is suppressed, and the oil unit 22 is protected from the temperature rise.

[0134] In addition, when the high temperature detection flag is set, the display process of S260 lights or flashes the notification LED provided on the display section 19 of the switch panel 18 to notify the user that the motor will stop due to a rise in temperature of the oil unit 22.

[0135] In the display process of S260, when an alarm is issued or a notification of motor stoppage is given, an alarm sound or notification sound may be given at the same time as lighting or blinking an LED provided on the display unit 19 of the switch panel 18. Also, for example, an alarm or a notification of motor stoppage may be given by blinking the light 14 in a predetermined pattern instead of an LED provided on the display unit 19 of the switch panel 18.

[0136] On the other hand, if it is determined in S390 that the number of strikes X is equal to or less than the temperature rise determination value Y, it is estimated that the number of strikes X is small and the temperature of the oil unit 22 will not rise, so the process proceeds to S410. In S410, the buffer into which the number of strikes X was written in S330 is updated by writing 0 as the strike count value, and the process proceeds to S420.

[0137] In S420, the index storing the number of the buffer to be updated is updated so that the buffer for which the number of hits will be updated next is set to the buffer next to the buffer updated this time, and the process proceeds to S430.

[0138] In addition, the processing of S420 is also executed when it is determined in S360 that the total number of impacts AD is equal to or less than the warning determination value TH1, or when it is determined in S380 that the total number of impacts AD is equal to or less than the high temperature determination value TH2.

[0139] Next, in S430, it is determined whether the high temperature detection flag is currently set. If it is determined in S430 that the high temperature detection flag is set, the process proceeds to S440, where it is determined whether a preset standby time has elapsed since the high temperature detection flag was set in S400.

[0140] If it is determined in S440 that the standby time has elapsed since the high temperature detection flag was set, the process proceeds to S450, where the high temperature detection flag and the warning request flag are cleared, and the protection process ends.

[0141] In addition, if it is determined in S430 that the high temperature detection flag is not set, or if it is determined in S440 that the standby time has not elapsed since the high temperature detection flag was set, the protection process is also terminated.

[0142] [effect] As described above, in the impact driver 1 of this embodiment, the frequency at which the protrusions 64, 64 of the rear case 51 collide with the blades 81, 81 in the oil unit 22 is calculated as the total number of impacts AD within a specified period using n buffers.

[0143] The sum AD is used as an estimated temperature value of the oil unit 22, and when the sum AD exceeds the high temperature determination value TH2, it is determined that the temperature of the oil unit 22 has risen, and the drive of the motor 20 is stopped. Therefore, it is possible to prevent the oil unit 22 from breaking down due to an oil leak or the like caused by a temperature rise in the oil unit 22.

[0144] Furthermore, when the total number of strikes AD calculated as the estimated temperature value of oil unit 22 exceeds a warning determination value TH1 that is lower than high temperature determination value TH2, a warning is issued to the user by lighting or flashing an LED. This allows the user to detect the temperature rise of oil unit 22 and suppress the temperature rise of oil unit 22 before microcomputer 100 stops driving motor 20.

[0145] Furthermore, the high temperature determination value TH2 and the warning determination value TH1 serving as protection thresholds are set lower as the ambient temperature increases, based on the temperature of the controller 16 detected by the temperature detection unit 130 immediately after startup of the microcomputer 100, in other words, the ambient temperature of the impact driver 1. Therefore, even in an environment where the ambient temperature is high and the oil unit 22 is prone to temperature increases, the temperature increase of the oil unit 22 can be detected more accurately, and the oil unit 22 can be protected from temperature increases.

[0146] Furthermore, when the total value AD calculated as the temperature estimation value becomes larger than the high temperature judgment value TH2 and the high temperature detection flag is set, the driving of the motor 20 is prohibited, but after the waiting time has elapsed, the high temperature detection flag is cleared and the driving of the motor 20 is permitted.

[0147] Therefore, by prohibiting the driving of the motor 20, the temperature rise of the oil unit 22 is suppressed, and then the oil unit 22 is cooled by the outside air, and when the temperature of the oil unit 22 drops, the driving of the motor 20 is automatically permitted. This allows the user to quickly resume work using the impact driver 1.

[0148] In this embodiment, the processes of S320 to S350 executed in the oil unit protection process correspond to the temperature estimation unit of the present disclosure, and the processes of S360 to S450 correspond to the protection operation unit of the present disclosure. Also, the motor control process of S250 shown in FIG. 7 corresponds to the motor control unit of the present disclosure.

[0149] [First Modification] In the present embodiment, the number of buffers used to calculate the total number of hits within a predetermined period AD as the estimated temperature value is n.

[0150] However, the number of impacts per operation differs between heavy load operation, in which a large load is applied to the motor 20 from the spindle 23 to which the tool bit is attached, and medium load operation, in which a smaller load is applied to the motor 20 than during heavy load operation. In other words, the number of impacts per operation during heavy load operation is greater than the number of impacts per operation during medium load operation.

[0151] For this reason, when each task is performed repeatedly, the time during which protection due to temperature rise is activated is shorter during heavy load tasks than during medium load tasks, and the total number of impacts detected within that time is lower during heavy load tasks than during medium load tasks.

[0152] Therefore, if the same number of buffers are used during heavy load work and medium load work to calculate the total number of impacts AD within the same period, it may not be possible to protect the oil unit 22 from temperature rise during heavy load work or medium load work.

[0153] Specifically, if the number of buffers and the judgment values ​​TH1 and TH2 are set assuming heavy-load work, the protection may not activate during medium-load work, causing the temperature of the oil unit 22 to rise to a dangerous temperature. Also, if the number of buffers and the judgment values ​​TH1 and TH2 are set assuming medium-load work, the time until the protection activates during heavy-load work may be longer, causing the temperature of the oil unit 22 to rise to a dangerous temperature.

[0154] Therefore, in this modification, two storage areas with different numbers of buffers, in other words, different periods for calculating the total number of impacts AD, are set in RAM 106. Specifically, the storage area with a smaller number of buffers is set as a storage area for the number of impacts for heavy-load work, and the storage area with a larger number of buffers is set as a storage area for the number of impacts for medium-load work.

[0155] Furthermore, two types of judgment values ​​are set for determining the temperature rise of the oil unit 22 from the total number of impacts AD stored in the buffer of each storage area: a judgment value for heavy load work and a judgment value for medium load work. The judgment value for heavy load work is set smaller than the judgment value for medium load work.

[0156] 8 is then executed using the two storage areas and judgment values. As a result, whether the work using the impact driver 1 is heavy-load work or medium-load work, a temperature rise in the oil unit 22 can be detected and protective action such as stopping the drive of the motor 20 can be appropriately performed.

[0157] [Second Modification] In this embodiment, when the high temperature detection flag is set, the motor control process at S250 is described as stopping the drive of the motor 20. However, when the motor 20 is operating without load, no impact occurs in the oil unit 22, so the temperature of the oil unit 22 does not rise. Furthermore, when the motor 20 is operating without load, the fan 35 rotates, which promotes cooling of the oil unit 22 and reduces the temperature of the oil unit 22.

[0158] For this reason, in the motor control process of S250, when the high temperature detection flag is set, the motor 20 may be allowed to operate without load. Note that the no-load operation of the motor 20 can be determined by whether the current flowing through the motor 20 is small or not.

[0159] Furthermore, in this way, if it is possible to perform no-load operation even if the high temperature detection flag is set in the motor control processing of S250, the waiting time used for the judgment in S440 may be switched depending on whether no-load operation is being performed or not.

[0160] In other words, if the motor 20 is operated in no-load mode while the high-temperature detection flag is set, the temperature of the oil unit 22 drops, allowing the motor 20 to resume normal operation in a short time. Therefore, when the motor 20 is operated in no-load mode, the standby time is made shorter than when the motor 20 is not operated in no-load mode. This improves the usability of the impact driver 1.

[0161] [Second embodiment] Next, in the above embodiment, the number of impacts counted every predetermined time T is stored in n buffers in sequence, and the estimated temperature value of the oil unit 22 is determined by calculating the total value AD of the number of impacts stored in each buffer.

[0162] However, this requires n buffers for storing the count values ​​of the number of hits in order, and cannot be realized if the memory capacity for n buffers cannot be secured in a memory such as the RAM 106.

[0163] Therefore, in this embodiment, the protection process for the oil unit 22 is executed according to the procedure shown in Fig. 10, whereby the number of impacts counted during the predetermined time T in the impact count measurement process of Fig. 7 is filtered to calculate a weighted average of the number of impacts. The calculation result is then used as an estimated temperature value of the oil unit 22 to determine whether the temperature of the oil unit 22 has risen and to perform protection process when the temperature rise is determined.

[0164] 10, in the protection process of this embodiment, similarly to the protection process shown in Fig. 8, it is determined in S310 whether a predetermined time T (for example, 1 second) has elapsed since the previous start of the process from S320 onwards. If it is determined in S310 that the predetermined time T has not elapsed, the protection process is terminated.

[0165] If it is determined in S310 that the predetermined time T has elapsed, the process proceeds to S320, and during the elapse of the predetermined time T, the number of hits is counted in the hit count measurement process of S230, and it is determined whether the number of hits has been updated to a value greater than 0.

[0166] If it is determined in S320 that the number of hits has been updated to a value greater than 0 during the lapse of the predetermined time T, the process proceeds to S332. In S332, a heat generation gain Kb that takes into account the temperature rise due to the hits is set as the filter gain K used to calculate the weighted average of the number of hits, and the process proceeds to S352. Note that in S332, the number of hits counted in S230 is set to an initial value of 0 so that the number of hits can be counted within the next predetermined time T.

[0167] If it is determined in S320 that the number of strikes has not been updated to a value greater than 0 within the predetermined time T, the process proceeds to S342. In S342, since the number of strikes is 0 and the oil unit 22 does not generate heat due to strikes, the heat dissipation gain Ka is set as the filter gain K used to calculate the weighted average of the number of strikes, and the process proceeds to S352.

[0168] The heat dissipation gain Ka and heat generation gain Kb are set so that the filter gain K is greater than 0 and less than 1. The heat dissipation gain Ka and heat generation gain Kb are set so that the temperature estimated value obtained by weighting the number of impacts corresponds to the number of impacts and the temperature change (actual measured value) of the oil unit 22 when impacts are actually generated.

[0169] Next, in S352, the weighted average value WA of the number of hits is calculated based on the following equation (1), which has as parameters the previously calculated weighted average value WAbf, the latest value An of the number of hits counted during the lapse of a predetermined time T, and a filter gain K.

[0170] WA = WAbf × (1 - K) + An × K … (1) In equation (1), the filter gain K is the heat radiation gain Ka or heat generation gain Kb that was set as the filter gain K in S332 or S342 this time.

[0171] In addition, in S352, the weighted average value WA is multiplied by an arbitrary Gain to calculate the temperature estimate value TE, and the process proceeds to S360, where the processes of S360 to S450 are executed in the same procedure as the protection process in the first embodiment. Note that in this embodiment, since there is no need to store the number of hits in the buffer, the processes of S390, S410, and S420 are not executed.

[0172] In this manner, in this embodiment, the estimated temperature value of the oil unit 22 is calculated by taking a weighted average of the number of strikes counted every predetermined time T. Therefore, unlike the first embodiment, there is no need to provide a buffer for storing past count values ​​of the number of strikes, and the storage capacity of memory such as RAM 106 used as a buffer can be reduced. This simplifies the configuration of the microcomputer 100 and reduces the cost of the controller 16.

[0173] [Third embodiment] 12, in the impact driver 1, when the motor 20 is driven under load, which causes an impact in the oil unit 22, the value of the current flowing through the motor 20 is larger than when the motor is driven without load, which does not cause an impact in the oil unit 22. Furthermore, the value of the current flowing through the motor 20 increases when an impact occurs.

[0174] Therefore, in this embodiment, instead of the number of impacts used to calculate the estimated temperature value in each of the above embodiments, the motor current detected by the current detection unit 120 is used to calculate the estimated temperature value of the oil unit 22. That is, in this embodiment, the microcomputer 100 executes the protection process for the oil unit in the procedure shown in Fig. 11. Note that in this embodiment, the process of measuring the number of impacts at S230 shown in Fig. 7 is not necessary.

[0175] 11, in the protection process for the oil unit 22 of this embodiment, as in the first embodiment, first, in S310, it is determined whether a predetermined time T has elapsed since the previous process of S320 or later was started. If it is determined in S310 that the predetermined time T has not elapsed, the process proceeds to S430.

[0176] If it is determined in S310 that the predetermined time T has elapsed, the process proceeds to S324, where it is determined whether the motor current acquired by the A / D conversion process in S220 has exceeded a preset current threshold value during the passage of the predetermined time T.

[0177] If it is determined in S324 that the motor current has exceeded the current threshold value during the predetermined time T, the process proceeds to S334. In S334, an integrated current value (= current value x time) is calculated based on the time during which the motor current exceeded the current threshold value during the predetermined time T and the current value of the motor current that exceeded the current threshold value, and the calculation result is saved in one of n buffers similar to those in the first embodiment.

[0178] This current integrated value can be calculated, for example, by storing the motor current values ​​acquired at predetermined time intervals in the A / D conversion process of S220. That is, in S334, current values ​​exceeding the current threshold are extracted from the current values ​​stored in the A / D conversion process over the predetermined time T, and the current integrated value is calculated from the extracted current values ​​and the sampling intervals of those current values.

[0179] However, this calculation method is just one example, and for example, instead of the hit count measurement process of 230, a current integrated value calculation process may be executed to sequentially integrate the current values ​​acquired in the A / D conversion process.

[0180] On the other hand, if it is determined in S324 that the motor current does not exceed the current threshold value within the predetermined time T, the process proceeds to S344. In S344, the integrated current value is set to "0" and stored in one of the n buffers, and the process proceeds to S354. The procedure for storing the integrated current values ​​in the n buffers is the same as in the first embodiment, and the n buffers store integrated current values ​​calculated within a period determined by the number of buffers n and the predetermined time T.

[0181] In S354, the total value AD of the current integrated values ​​stored in the n buffers is calculated as the estimated temperature value of the oil unit 22. Then, the processes of S360 to S450 are executed in the same procedure as the protection process of the first embodiment, and the protection process ends.

[0182] In this way, in this embodiment, the current cumulative value is calculated every predetermined time T, and the total value AD as the estimated temperature value of the oil unit 22 is calculated by adding up the current cumulative values ​​calculated within a predetermined period determined by the number of buffers: n.

[0183] Therefore, in this embodiment, as in the first embodiment, the processing from S360 onwards detects a temperature rise in the oil unit 22, and the oil unit 22 can be protected from the temperature rise.

[0184] [Other embodiments] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms.

[0185] For example, even if the first or second modified example of the first embodiment is applied to the second or third embodiment, the same effects as those of the first or second modified example can be obtained.

[0186] Furthermore, the configuration of the oil unit 22 described in the above embodiment is merely an example, and for example, the impact mechanism may be configured to push the blade 81 radially outward only by the biasing force of the coil spring 78. Alternatively, the impact mechanism may be configured to push the blade 81 radially outward only by the movement of the ball 85 caused by the rotation of the cam 66. Furthermore, other elastic members may be used instead of the coil spring 78.

[0187] Furthermore, the motor 20 is not limited to a three-phase brushless motor, but may be a single-phase or other brushless motor, or a commutator motor. The rotary impact tool is not limited to an impact driver in which the spindle 23 of the oil unit 22 serves as the output shaft. For example, it may be an angle type in which the final output shaft is disposed perpendicularly in front of the spindle 23. The rotary impact tool may also be an AC tool that does not use the battery pack 5 as its power source.

[0188] The controller 16 may also be implemented by a special-purpose computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the controller 16 may be implemented by one or more special-purpose computers configured by combining a processor and memory programmed to perform one or more functions with a processor configured with one or more hardware logic circuits. A computer program may also be stored on a computer-readable non-transitory tangible recording medium as instructions to be executed by a computer. The method for implementing the functions of each unit included in the controller 16 does not necessarily need to include software; all of the functions may be implemented using one or more pieces of hardware.

[0189] In the above embodiments, multiple functions of one component may be realized by multiple components, or one function of one component may be realized by multiple components. Furthermore, multiple functions of multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Furthermore, part of the configuration of the above embodiments may be omitted. Furthermore, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0190] In addition to the rotary impact tool described above, the present disclosure can also be realized in various forms, such as a system including a rotary impact tool as a component, a program for causing a computer to function as a rotary impact tool, a non-transient physical recording medium such as a semiconductor memory on which this program is recorded, and a temperature protection method for an oil unit.

[0191] [Technical idea disclosed in this specification] [Item 1] A motor; An output shaft to which a tool can be attached, an oil unit including: a case rotated by the motor and into which the rear end side of the output shaft is rotatably inserted; oil sealed in the case; and an impact mechanism configured to transmit the rotational torque of the case to the output shaft by the oil to rotate the output shaft, and to form a high-pressure chamber for the oil by a rotational phase difference between the case and the output shaft to impact the output shaft; a motor control unit configured to drive and control the motor in accordance with an external command; an impact state measuring unit configured to measure an impact state of the output shaft by the impact mechanism; a temperature estimation unit that estimates a temperature of the oil unit by integrating the measurement results of the impact state by the impact state measurement unit; a protection operation unit configured to perform a protection operation of suppressing driving of the motor by the motor control unit when the temperature estimated value obtained by the temperature estimator exceeds a predetermined protection threshold; A rotary impact tool comprising:

[0192] [Item 2] The rotary impact tool according to item 1, the impact state measurement unit is configured to measure the number of impacts per predetermined time as the impact state; The temperature estimation unit is configured to estimate the temperature of the oil unit by accumulating the number of impacts measured by the impact state measurement unit.

[0193] [Item 3] The rotary impact tool according to item 2, The temperature estimation unit is configured to reduce the integrated value of the number of impacts when the number of impacts measured by the impact state measurement unit is equal to or less than a preset lower limit number.

[0194] [Item 4] Item 3. The rotary impact tool according to item 3, The temperature estimation unit a plurality of buffers configured to store the number of hits measured by the hitting state measuring unit; Each time the impact count per predetermined time is measured by the impact state measurement unit, the measured impact count is stored in the plurality of buffers in order, thereby updating the impact count in each buffer in order; calculating a total number of impacts stored in the plurality of buffers as an estimated temperature value of the oil unit; The rotary impact tool is configured as follows.

[0195] [Item 5] Item 4: A rotary impact tool according to item 4, the temperature estimation unit includes two buffer groups each having a different number of buffers, and stores the number of impacts and calculates the total number of impacts for each buffer group; the protective operation unit is configured to compare the total number of impacts calculated by the temperature estimation unit using the two buffer groups with a protection threshold value set in advance for each buffer group, and to perform the protective operation when either of the total numbers of impacts exceeds a corresponding protection threshold value.

[0196] [Item 6] The rotary impact tool according to item 4 or 5, The protective operation unit is configured to determine whether the latest value of the number of impacts stored in the multiple buffers is equal to or less than a predetermined lower limit number when the total number of impacts stored in the multiple buffers exceeds the protection threshold, and not to perform the protective operation when the latest value of the number of impacts is equal to or less than the lower limit number.

[0197] [Item 7] The rotary impact tool according to item 1, the impact state measurement unit is configured to measure the number of impacts per predetermined time as the impact state; The temperature estimation unit estimates the temperature of the oil unit by taking a weighted average of the number of impacts measured by the impact state measurement unit, and is configured to switch a gain used for the weighted average depending on whether the number of impacts is equal to or greater than a threshold value.

[0198] [Item 8] The rotary impact tool according to item 1, the impact state measurement unit is configured to measure, as the impact state, a current flowing through the motor per predetermined time; The temperature estimation unit is configured to estimate the temperature of the oil unit by integrating the current measured by the impact state measurement unit.

[0199] [Item 9] Item 8. A rotary impact tool according to item 8, The rotary impact tool, wherein the temperature estimation unit is configured not to integrate the current when the current measured by the impact state measurement unit is equal to or lower than a preset lower limit current.

[0200] [Item 10] A rotary impact tool according to any one of items 1 to 9, The protective operation unit is configured to prohibit the motor control unit from driving the motor as the protective operation.

[0201] [Item 11] Item 11. A rotary impact tool according to item 10, The protective operation unit is configured to notify the user that the protective operation is being performed when the protective operation prohibits the motor control unit from driving the motor.

[0202] [Item 12] A rotary impact tool according to any one of items 1 to 9, The protective operation unit is configured to perform the protective operation by notifying an increase in temperature of the oil unit.

[0203] [Item 13] A rotary impact tool according to any one of items 1 to 12, The protective operation unit is configured to cancel the implementation of the protective operation when a preset waiting time has elapsed since the protective operation was started.

[0204] [Item 14] A rotary impact tool according to any one of items 1 to 13, A rotary impact tool comprising: a protection threshold setting unit configured to set the protection threshold in accordance with an ambient temperature of the rotary impact tool.

[0205] [Item 15] Item 15. The rotary impact tool according to item 14, The protection threshold setting unit is configured to set the protection threshold in accordance with an ambient temperature at the time of activation of the rotary impact tool. [Explanation of symbols]

[0206] 1...impact driver, 16...controller, 20...brushless motor, 22...oil unit, 23...spindle, 29A...rotational position detection unit, 50...front case, 51...rear case, 64...protrusion, 66...cam, 67...internal pressure chamber, 78...coil spring, 81...blade, 85...ball, 100...microcomputer, 120...current detection unit.

Claims

1. A motor; An output shaft to which a tool can be attached, an oil unit including: a case rotated by the motor and into which the rear end side of the output shaft is rotatably inserted; oil sealed in the case; and an impact mechanism configured to transmit the rotational torque of the case to the output shaft by the oil to rotate the output shaft, and to form a high-pressure chamber for the oil by a rotational phase difference between the case and the output shaft to impact the output shaft; a motor control unit configured to drive and control the motor in accordance with an external command; an impact state measurement unit configured to measure an impact state of the output shaft by the impact mechanism; a temperature estimation unit that estimates a temperature of the oil unit by integrating the measurement results of the impact state by the impact state measurement unit; a protection operation unit configured to perform a protection operation of suppressing driving of the motor by the motor control unit when the temperature estimated value obtained by the temperature estimator exceeds a predetermined protection threshold; A rotary impact tool comprising:

2. The rotary impact tool according to claim 1, the impact state measurement unit is configured to measure the number of impacts per predetermined time as the impact state; The temperature estimation unit is configured to estimate the temperature of the oil unit by accumulating the number of impacts measured by the impact state measurement unit.

3. The rotary impact tool according to claim 2, The temperature estimation unit is configured to reduce the integrated value of the number of impacts when the number of impacts measured by the impact state measurement unit is equal to or less than a preset lower limit number.

4. The rotary impact tool according to claim 3, The temperature estimation unit a plurality of buffers configured to store the number of hits measured by the hitting state measuring unit; Each time the impact count per predetermined time is measured by the impact state measurement unit, the measured impact count is stored in the plurality of buffers in order, thereby updating the impact count in each buffer in order; calculating a total number of impacts stored in the plurality of buffers as an estimated temperature value of the oil unit; The rotary impact tool is configured as follows.

5. The rotary impact tool according to claim 4, the temperature estimation unit includes two buffer groups each having a different number of buffers, and stores the number of impacts and calculates the total number of impacts for each buffer group; The protective operation unit is configured to compare the total number of impacts calculated by the temperature estimation unit using the two systems of buffer groups with a protection threshold value set in advance for each buffer group, and to perform the protective operation when either of the total numbers of impacts exceeds a corresponding protection threshold value.

6. The rotary impact tool according to claim 4, The protective operation unit is configured to determine whether the latest value of the number of impacts stored in the multiple buffers is equal to or less than a predetermined lower limit number when the total number of impacts stored in the multiple buffers exceeds the protection threshold, and not to perform the protective operation when the latest value of the number of impacts is equal to or less than the lower limit number.

7. The rotary impact tool according to claim 1, the impact state measurement unit is configured to measure the number of impacts per predetermined time as the impact state; The temperature estimation unit estimates the temperature of the oil unit by taking a weighted average of the number of impacts measured by the impact state measurement unit, and is configured to switch a gain used for the weighted average depending on whether the number of impacts is equal to or greater than a threshold value.

8. The rotary impact tool according to claim 1, the impact state measurement unit is configured to measure, as the impact state, a current flowing through the motor per predetermined time; The temperature estimation unit is configured to estimate the temperature of the oil unit by integrating the current measured by the impact state measurement unit.

9. The rotary impact tool according to claim 8, The rotary impact tool, wherein the temperature estimation unit is configured not to integrate the current when the current measured by the impact state measurement unit is equal to or lower than a preset lower limit current.

10. The rotary impact tool according to any one of claims 1 to 9, The protective operation unit is configured to prohibit the motor control unit from driving the motor as the protective operation.

11. The rotary impact tool according to claim 10, The protective operation unit is configured to notify the user that the protective operation is being performed when the protective operation prohibits the motor control unit from driving the motor.

12. The rotary impact tool according to any one of claims 1 to 9, The protective operation unit is configured to perform the protective operation by notifying an increase in temperature of the oil unit.

13. The rotary impact tool according to any one of claims 1 to 9, The protective operation unit is configured to cancel the implementation of the protective operation when a preset waiting time has elapsed since the protective operation was started.

14. The rotary impact tool according to any one of claims 1 to 9, A rotary impact tool comprising: a protection threshold setting unit configured to set the protection threshold in accordance with an ambient temperature of the rotary impact tool.

15. The rotary impact tool according to claim 14, The protection threshold setting unit is configured to set the protection threshold in accordance with an ambient temperature at the time of activation of the rotary impact tool.

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